Colonization of fouling communities and associated fauna on artificial reef at Ranong Province, Thailand

Artificial reef (AR3) installed at 10 km off Ban Kampuan's coast, Ranong Province in 1989 was observed in February 1992 (first observation), December 1992 (second observation) and April 1993 (third observation). The objective of the study was to observe the development of fouling communities and associated fauna on the reef concrete surfaces in different period of time. The results showed the occurrence of the benthic organisms of 7 Phyla, namely Porifera, Coelenterata, Annelida, Echinodermata, Mollusca, Arthropoda and Chordata. The total biomass on the under surface of the module was higher than those on the vertical and top surfaces respectively. The biomass also varied in different time of observation. Saccostrea spp., The most abundant group were the major contributor to the reef structure and were the main factor that influenced a change of total biomass. Total biomass in the first observation was highest and statistically different from the second and third observation. This indicated the succession stage of the Saccostrea that might has already reached the equilibrium during the first observation. The biomass fluctuation, especially from the under and vertical surfaces may due to the overweight of the aggregated organisms which then gradually collapsed and dropped on sea floor. The additional experiment on setting plates revealed the early stage (4 month period) of organism development on the new substrates. Thin layer of filamentous algae and bryozoa accounted for the highest area cover. The total biomass were much greater than those reported from the coral reefs down south. It could be concluded that the AR3 was a productive system, since there was an occurrence of the second production of the important benthic organisms especially the small cryptic fauna those although contributed a low biomass, but were high in number, i.e. polychaetes, crabs, shrimps, isopods and brittle stars. The reef was still in a process of undergoing change to the oyster reef. Thus future study on the development of the benthos communities on the sea bottom in this area would be of interest.